FSO (Free Space Optics) systems are a novel wireless transmission system, which can transmit signals via light and the transmission medium thereof is air. FSO systems can be swiftly installed without complicated wiring and can be reused after being recovered, so are very suitable for temporary mobile network systems. Therefore, FSO systems have become the best solution in the last mile of metropolitan area networks.
A currently available FSO system usually includes several optical antennas. In general, a currently available optical antenna includes a light signal emitter and a light signal receiver. The optical antenna and a target antenna should be disposed at the same plane. Besides, the light signal emitter of the optical antenna should aim at the light signal receiver of the target antenna so as to transmit signal lights thereto. Similarly, the light signal receiver of the optical antenna should aim at the light signal emitter of the target antenna so as to receive signal lights therefrom.